Antenna Installation Tolerances

When designing or even installing antenna systems for a wireless communication
facility, the installation will have some variance to the design. Just what variances are enabled needs to be stipulated from the onset of the
design process. The antenna installation tolerances apply directly to the
physical orientation and plumbness of the antenna installation itself. There
are usually two separate requirements: how accurate should the antenna
orientation be and how plumb should the antenna installation be. The obvious issue here is not only the design requirements from engineering but
also the practical implementation of the antennas for cost reasons.
Therefore, the following guidelines in Table 11-1 should be used.
The antenna orientation tolerance is a function of the antenna pattern
and can be unique for each type of cell site. Obviously, for an omni cell site,
there are no orientation requirements because the site is meant to cover
360 degrees. However, for a sector or directional cell site, the orientation tolerance
becomes a critical issue. The orientation tolerance should be specified
from Radio Frequency (RF) engineering but in the absence of this, the
guideline is to be within 5 percent of the antennas horizontal pattern.Table
11-2 will help illustrate the issue by using some of the more standard types
of antenna patterns used in the industry.
The obvious goal however is to have no error associated with the orientation
of the antenna, but this is rather impractical.
Therefore, as the antenna pattern becomes more tight, the tolerance for
the orientation error is reduced. The objective defined here is / 5 percent,
but the number can be either relaxed or tightened depending on your
particular system requirements. The 5 percent number should also factor into any potential building sway that can and does occur, usually a nonissue
due to the height of the buildings used for wireless installations.